UNIVERSITY    OF    CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL    EXPERIMENT    STATION 

CIRCULAR  No.  214 


SEED   TREATMENT 

FOR  THE 

PREVENTION   OF  CEREAL  SMUTS 

By  W.  W.  MACKIE* 


The  excessive  demand  for  all  cereals  has  given  great  stimulus  to 
cereal  production.  The  extensive  use  of  tractors  in  California  has 
made  better  cultivation  possible,  greatly  assisting  in  the  maintenance 
of  high  yields.  Increased  yields,  however,  do  not  follow  better  cultiva- 
tion unless  the  crops  are  free  from  diseases,  the  most  persistent  of 
which  are  the  smuts.  Cereal  smuts  occur  every  year,  causing  very 
considerable  damage  which  may  vary  according  to  the  weather  and 
the  efforts  of  the  farmers  to  prevent  it. 

During  the  season  of  1918  actual  field  counts  showed  the  loss  from 
stinking  smut  of  wheat  in  California  to  be  5.8  per  cent  of  the  total 
crop,  or  461,173  bushels.  The  estimated  loss  from  wheat  smut  for  the 
crop  of  1917  was  8  per  cent.  Calculations  for  smut  in  wheat  losses  for 
the  1919  crop,  although  not  completed,  place  the  average  damage  at 
about  2  per  cent.  This  loss  does  not  include  plants  which  have  been 
killed  by  the  attack  of  smut  before  maturity.  This  great  reduction  in 
smut  losses  is  apparently  due  primarily  to  the  campaign  waged  against 
smuts  since  September,  1917,  to  induce  grain  growers  to  practice 
more  universal  and  better  seed  treatment  methods  to  overcome  smut 
diseases  in  cereals. 

How  Smut  Grows. — Cereal  smuts  are  caused  by  fungus  parasites 
which  are  propagated  by  means  of  spores.  They  are  divided  into  two 
general  classes  according  to  the  manner  in  which  they  attack  the  cereal 
plant,  viz.,  the  covered,  or  kernel  smuts  which  leave  the  kernel  in  a 
more  or  less  solid  ball  similar  in  shape  to  the  original  seed;  and  the 
loose  smuts  which  entirely  destroy  the  head,  disintegrating  it  into  a 
mass  of  loose  black  spores  which  readily  fall  apart  and  are  blown 
about  by  the  wind.  The  attack  in  the  cereal  plant  of  each  class  of 
smut  differs  completely.     The  kernel  smuts   (bunt,  covered  smut  of 

*  University  of  California,  and  the  Office  of  Cereal  Investigations,  United 
States  Department  of  Agriculture  cooperating. 


barley,  hidden  smut  of  oats,  etc.)  are  carried  on  the  outside  of  the 
seed  into  the  soil  at  planting  time.  The  only  exception  is  bunt,  which 
may  also  infect  the  wheat  plant  from  the  soil.  In  that  case  the  smut 
spores  germinate  at  the  same  time  as  grain  seed  and  by  putting  forth 
a  thin  mycelial  thread  pierce  the  young  cereal  seedling.  The  parasite 
then  continues  to  grow  within  the  host  until  the  seed  begins  to  form. 
At  this  time  the  parasite  consumes  all  the  starch  of  the  kernel,  trans- 
forming it  into  a  mass  of  smut  spores.  This  class  of  spores  is  destroyed 
by  dipping  the  seed  in  fungicidal  solutions. 

The  loose  smuts  of  cereals  make  their  attack  at  the  time  the  grain 
is  in  flower.  At  this  time  the  loose  smut  spores  are  being  blown  about 
in  the  air  and  some  find  lodgment  in  the  flower  of  the  cereal  where  they 
germinate  at  once  and  send  their  threads  into  the  germ  of  the  kernel. 
When  the  kernel  matures  and  hardens,  the  smut  becomes  dormant  and 
remains  in  this  condition  until  the  seed  is  planted.  When  the  seed 
germinates,  the  smut  begins  to  grow.  The  smut  parasite  then  con- 
tinues its  growth  inside  the  host  plant,  maturing  just  as  the  grain 
comes  into  flower.  By  its  peculiar  method  of  growth  the  loose  smut 
spore  is  never  exposed  on  the  outside  of  the  seed  and  consequently 
cannot  be  destroyed  by  dipping  the  seed  in  fungicides.  It  can  only 
be  destroyed  by  heat  when  dipped  in  hot  water.  This  method  is  very 
difficult  to  apply  on  account  of  the  small  differences  in  the  degrees 
of  heat  which  will  kill  the  smut  spores  and  that  which  will  kill  the 
germ  of  the  seed.  Fortunately,  the  damage  from  loose  smuts  in  wheat, 
barley,  and  oats  in  California  is  so  slight  that  these  smuts  are  not 
considered  of  economic  importance. 

Classification  of  Cereal  Smuts. — 

Covered  Smuts. — Bunt  or  stinking  smut  of  wheat  (Tilletia  tritici  and  T. 
laevis) ;  covered  smut  of  barley  (Ustilago  hordei)  ;  hidden  smut  of  oats  (Ustilago 
levis)  ;  kernel  smut  of  sorghum  (Sphacelotheca  sorghi)  ;  ergot  of  rye  (Claviceps 
purpurea) . 

Loose  Smuts. — Loose  smut  of  wheat  (Ustilago  tr'itici)  ;  loose  smut  of  barley 
(Ustilago  nuda) ;  loose  smut  of  oats  (Ustilago  avcivac) ;  corn  smut  (Ustilago 
zeae). 

This  list  of  smuts,  though  formidable  in  number,  may  be  reduced 
to  three  that  are  causing  serious  damage  to  cereal  crops  in  California, 
namely:  stinking  smut  of  wheat,  covered  smut  of  barley,  and  corn 
smut.  Corn  smut  may  be  prevented  only  by  eradicating  diseased 
plants  at  once  on  their  appearance.    Seed  treatment  offers  no  remedy. 

Kernel  smut  of  sorghum,  Sudan  smut,  hidden  smut  of  oats  and 
covered  smut  of  barley  are  controlled  by  the  use  of  formaldehyde. 
Stinking  smut  of  wheat,  or  bunt,  is  controlled  by  the  same  fungicide 
where  no  soil  infestation  from  bunt  spores  occurs. 


Soil  Infestation  from  Bunt. — Due  to  the  rainless  summers  of  Cali- 
fornia and  other  states  of  the  Pacific  Coast,  the  bunt  spores  are  not 
attacked  by  the  ferments  and  fungus  parasites  which  may  destroy 
the  bunt  spores  in  the  humid  eastern  states.  When  smutty  wheat  fields 
are  threshed,  the  spores  are  scattered  over  the  soil  and  may  be  blown 
over  many  miles  to  be  deposited  in  fields  where  theretofore  the  crops 
may  have  been  free  from  smut.  Summer-fallowed  fields  are  especially 
liable  to  smut  infection  through  wind-blown  bunt  spores,  for  the  soil 
is  not  deeply  tilled  before  seeding  the  crop.  Bunt  spores  require  about 
14  per  cent  of  moisture  in  the  soil  or  a  moist  atmosphere  for  germina- 
tion. If  the  temperature  is  much  above  65°  F.  the  spores  do  not 
germinate,  although  they  will  survive  a  much  higher  temperature  for 
a  brief  period  in  midday,  provided  the  temperature  is  below  65°  F. 
for  the  remainder  of  the  twenty-four  hours.  With  favorable  moisture 
and  temperature  conditions  bunt  spores  may  germinate,  grow  and 
develop  in  soil  solutions  for  a  considerable  period,  perhaps  six  weeks 
or  longer,  without  a  wheat  host  plant.  When  seed  is  sown  in  such 
infested  soil,  the  wheat  seedling  is  liable  to  attack  until  after  it 
emerges  from  the  soil.  With  the  emergence  of  the  growing  point  of 
the  seedling  into  the  air,  it  becomes  immune  from  attack  because  the 
smut  fungus  thread  appears  not  to  be  able  to  attack  the  seedling  after 
it  appears  above  ground.  It  is  because  of  the  antagonism  of  the  blue- 
stone  which  remains  on  the  wheat  seed,  that  this  fungicide  gives  a 
certain  amount  of  immunity  from  attack  until  the  growing  seedling 
passes  out  of  the  soil  solution  charged  with  the  bluestone.  If  the 
seedling  is  close  to  the  soil  surface  or  if  the  soil  moisture  and  tem- 
perature are  not  favorable  to  the  growth  of  the  smut  mycelium,  the 
wheat  seedling  may  escape  attack.  Formaldehyde  is  less  effective 
against  soil  infection  because  the  formaldehyde  evaporates  rapidly 
from  the  seed.  Soil  infestation  by  bunt  spores  accounts  for  many  appar- 
ent failures  of  seed  treatment  both  by  bluestone  and  formaldehyde,  to 
eradicate  stinking  smut  in  wheat.  Both  of  these  fungicides  are 
effective  against  seed  borne  bunt  spores  and  spores  of  other  covered 
smuts,  especially  covered  smut  of  barley  which  appears  to  be  incapable 
of  causing  soil  infestation. 

Soil  infestation  from  bunt  spores  appears  to  be  confined  to  the 
areas  away  from  the  coast  where  the  air  usually  carries  only  a  small 
amount  of  moisture  in  the  summer.  The  interior  valleys  are  subject 
to  this  trouble,  but  soil  infestation  is  not  always  certain,  and  there 
is  evidence  that  some  areas  may  not  be  affected.  Variation  in  the 
occurrence  of  the  first  and  second  rains  of  the  season  may  cause  great 
variation  in  soil  infestation.  Early  rains  may  germinate  smut  spores 
in  the  soil  which  may  die  out  later  for  lack  of  moisture  or  host  plants. 


Soils  may  be  moist  enough  to  sprout  the  wheat  while  too  dry  to 
germinate  bunt  spores.  In  this  way  wheat  seedlings  emerge  from 
the  soil  free  from  attack.  Late  sown  wheat,  when  the  seed  is  carefully 
treated,  usually  escapes  with  little  or  no  smut,  even  in  soils  where  soil 
infestation  has  been  found  in  the  preceding  fall.  Very  late  sown 
wheat  planted  when  the  spring  weather  is  too  warm  for  the  germina- 
tion of  bunt  spores  may  escape  smut  attack  even  when  smutty  seed  is 
sown.  Late  sowing  of  wheat,  however,  as  a  rule,  results  in  poor  yields. 
The  best  results  are  secured  by  sowing  early  with  seed  which  has  been 
treated  to  destroy  the  smut  spores. 

Fungicides  Used  to  Control  Smut. — Bluestone  solutions  have  been 
used  to  destroy  smut  spores  in  wheat  seed  for  nearly  a  century.  Tn 
California  bluestone  formulas  have  given  the  best  results  because  of 
the  liability  of  soil  infestation  from  bunt  spores  and  because  of  the 
practice  of  seeding  in  dry  soil  for  which  these  formulas  are  well 
adapted. 

Formula  for  Bluestone-Lime   Treatment 

1.  Dissolve  1  pound  of  bluestone  (copper  sulphate)  in  4  gallons  of  water 
which  must  be  held  in  a  wooden  trough  or  tub. 

2.  Dip  the  seed  contained  in  half  sacks  or  butts  for  3  to  5  minutes  in  the 
bluestone  solution.     Shake  out  the  air  as  the  sacks  soak. 

3.  Drain  the  sacks  for  15  minutes  and  then  dip  in  a  lime  solution  prepared  by 
slaking  1  pound  of  quick-lime  in  8  gallons  of  water.  If  the  lime  solution  becomes 
blue,  replenish  with  a  new  solution. 

4.  Dry  thoroughly  before  storing. 

When  barley  is  treated  with  this  solution  or  when  the  lime  dip  is  not  used  after 
the  bluestone  treatment,  use  1  pound  of  bluestone  to  5  gallons  of  water.  Wash 
seed  in  water  before  dipping  in  bluestone  where  the  lime  dip  is  omitted. 

Instructions. — Wash  out  smut  balls.  If  the  seed  wheat  contains 
smut  balls  they  should  be  washed  out  before  dipping  the  seed  in  the 
bluestone.  If  the  wheat  is  poured  slowly  into  a  receptacle  containing 
water  and  stirred,  the  smut  balls  may  be  skimmed  off  as  they  rise  to 
the  surface  together  with  chaff,  etc.  A  smut-cleaning  machine  is  sold 
which  performs  this  task  automatically.  Washing  out  smut  balls 
should  not  be  neglected,  for  no  bluestone  or  formaldehyde  solution 
will  penetrate  the  smut  balls  or  smut  masses  sufficiently  to  destroy 
the  smut  spores  without  severe  injury  to  the  seed  germ.  With  the 
washing  out  of  the  smut  balls  the  water  tends  to  disperse  and  wet  the 
remaining  spores.  After  this  washing  the  immersion  of  the  seed  in 
the  bluestone  solution  gives  better  results  in  destroying  the  smut 
spores  which  are  softened  by  the  water  and  thus  rendered  more 
susceptible  to  the  effects  of  the  fungicide.    Also  the  seed  wheat,  being 


saturated  with  water,  excludes  excessive  quantities  of  bluestone  which 
might  otherwise  enter  the  seeds  through  broken  or  injured  seed-coats, 
causing  death  or  delayed  germination  of  the  seed  germ. 

Smut  balls  left  in  the  seed  wheat  are  a  source  of  reinfection  be- 
cause, on  account  of  their  oily  constitution,  they  are  not  readily  pene- 
trated and  destroyed  by  the  fungicidal  solutions.  Frequently  the  balls 
are  broken  by  the  drill  or  broadcaster  in  the  operation  of  seeding.  When 
not  broken  the  smut  balls  are  seeded  into  the  soil  where  they  may  send 
out  mycelial  threads  from  live  spores  germinating  within  the  interior 
of  the  ball.  As  each  smut  ball  contains  about  four  million  spores  a 
very  few  balls  are  capable  of  infecting  a  large  number  of  seeds.  A 
bushel  of  wheat  contains  from  600,000  to  1,000,000  kernels.  Seed 
wheat  which  is  very  smutty  should  not  be  used  for  seed  as  it  is  fre- 
quently impossible  to  destroy  all  the  smut  spores  on  a  seed  which  is 
visibly  darkened  with  the  smut  spores.  Such  a  seed  may  contain 
thousands  of  spores  on  its  surface.  Masses  of  spores  grouped  in  the 
brush  end  and  the  creases  of  the  seed  hold  small  bubbles  of  air  which 
do  not  permit  the  fungicide  to  reach  the  spores.  These  spores  may 
remain  viable  even  in  strong  solutions,  later  to  become  a  source  of 
smut  infection. 

How  to  Test  the  Strength  of  the  Bluestone  Solution. — The  solution 
of  bluestone  should  be  kept  at  the  prescribed  strength.  If  it  is  stronger 
than  required,  the  danger  of  injury  to  the  seed  germ  is  increased,  and 
if  much  weaker,  the  solution  fails  to  destroy  all  the  smut  spores. 

The  use  of  the  brix  sugar  hydrometer  is  recommended  in  determin- 
ing the  strength  of  the  bluestone  solution.  This  hydrometer  can  be 
furnished  by  any  large  chemical  supply  house  for  a  small  price.  As 
the  density  of  the  solution  changes  with  the  temperature,  the  simplest 
method  of  securing  the  correct  reading  with  the  hydrometer  consists 
in  floating  the  hydrometer  in  a  cylindrical  vessel  containing  the 
standard  solution  carefully  prepared  by  weighing  the  bluestone  and 
accurately  measuring  the  water.  When  the  bluestone  is  dissolved  the 
hydrometer  will  give  a  certain  reading  on  the  scale  at  the  surface  of 
the  solution.  The  bluestone  solution  in  the  wooden  trough  should 
read  exactly  the  same.  If  the  hydrometer  sinks  into  the  bluestone 
solution  submerging  the  measured  reading,  the  solution  is  too  weak 
and  should  be  strengthened  by  dissolving  into  it  more  bluestone  by 
suspending  a  grain  sack  containing  bluestone  in  one  end  of  the  trough. 
If  the  reading  rises  into  the  air  the  solution  is  too  strong  and  should 
be  diluted  with  water  until  the  correct  reading  reaches  the  surface. 

Dipping  Bluestoned  Seed  in  Lime  Solution. — Fifteen  minutes  is 
given  as  the  usual  length  of  time  for  draining  the  dipped  seed.  As 
long  as  the  seed  is  wet  the  fungicide  is  still  active.     After  draining 


about  15  minutes  the  bluestoned  wheat  should  now  be  dipped  into  the 
lime  solution  in  order  to  check  the  injurious  effect  of  the  bluestone  on 
the  germ  of  the  seed.  This  the  lime  does  effectively  for  all  but  seeds 
with  badly  injured  seed-coats.  Strong  bluestone  solutions  sufficient 
to  kill  the  spores  (1  pound  of  bluestone  to  4  to  5  gallons  of  water) 
have  been  found,  by  testing  hundreds  of  samples  collected  on  farms 
over  the  state,  to  kill  on  the  average  60  per  cent  of  the  seed.  This 
loss  is  almost  entirely  eliminated  by  the  lime  dip.  In  addition  the 
lime  causes  the  seedling  to  make  a  more  rapid  start  which  is  plainly 
evident  by  contrast  where  bluestone  alone  is  used.  Where  no  lime 
is  used  the  rootlets  are  delayed  long  after  the  plumule  has  made  a 
good  growth.  The  rootlets  should  naturally  develop  first.  This  the 
lime  assists  the  roots  to  do.  Lime  coated  over  the  seed  tends  to  delay 
drying.  This  may  lead  to  heating  of  the  seed  if  stored  before  it  is 
thoroughly  dried.  When  dipping  operations  are  carried  on  in  cold, 
damp  weather,  care  should  be  taken  to  keep  the  butts  or  sacks  of  seed 
separated  or  spaced  in  open,  well  ventilated  sheds. 

Dry  the  Lime-Treated  Seed. — To  avoid  the  possibility  of  injury 
due  to  slow  drying  the  seed  wheat  should  be  cleaned  and  dipped  soon 
after  harvest  when  the  weather  is  dry  and  warm.  At  this  time  the  seed 
can  be  rapidly  and  thoroughly  dried  and  then  placed  in  the  granary 
awaiting  the  seeding  time.  Tests  show  no  more  deterioration  for  seed 
wheat  treated  with  the  bluestone-lime  dip  after  having  been  kept  for 
two  years,  than  for  untreated  seed  from  the  same  lot  of  wheat  or 
barley. 

Bluestone  Injury  Caused  by  Broken  Seed  Coats. — Seed  injury 
from  bluestone  may  be  traced  usually  to  injury  of  the  seed  coat. 
When  grain  is  threshed  with,  the  cylinder  running  too  close  much 
injury  to  the  seed  coat  results.  When  seed  wheat  is  recleaned  with 
powerfully  driven  machinery  it  is  frequently  badly  injured,  especially 
over  the  germ  where  the  seed  coat  is  softer  and  much  wrinkled  and 
therefore  more  easily  torn.  Through  these  ruptures  the  bluestone  pene- 
trates readily  and  injury  to  the  germ  results.  In  ordinary  threshing  and 
harvesting  the  majority  of  the  wheat  kernels  are  scratched  or  slightly 
injured.  These  injuries  need  cause  no  concern  when  lime  is  used 
after  the  bluestone.  A  small  hand  lens  will  readily  show  the  ruptures 
which  may  occur  over  the  germ.  Severe  recleaning  may  be  detected 
when  the  hairs  which  occur  on  the  brush  end  of  the  kernel  have  been 
scoured  away.  Wheat  seed  with  perfect  seed  coats  has  shown  no  injury 
when  soaked  for  six  hours  in  a  concentrated  solution  of  bluestone. 

The  bluestone-lime  dip  has  been  in  use  in  Australia  for  many  years, 
where  it  has  established  its  superiority  over  the  formaldehyde  solution 
or  bluestone  when  used  without  the  lime  dip. 


Sprinkling  Bluestone  Solutions  on,  Seed. — Bluestone  in  solutions 
of  standard  strength  may  be  sprinkled  on  loose  seed  wheat  if  the 
wheat  is  constantly  stirred  to  thoroughly  wet  all  the  seed  surface. 
This  process  appears  to  give  less  injury  to  germination  than  the  dip- 
ping, but  greater  care  is  required  in  the  mixing  of  the  seed  and  solu- 
tion in  order  to  thoroughly  wet  all  the  seed.  An  auger  elevator,  such 
as  used  in  flour  mills,  has,  in  one  instance,  been  operated  successfully 
to  mix  seed  wheat  with  a  strong  solution  of  bluestone  which  was 
steadily  dripping  on  the  moving  wheat. 

Treatment  with  Formaldehyde  Solution 

Formula:  Formaldehyde  (U.  S.  P.  37  per  cent),  1  pint  to  40  gallons  of  water; 
soak  the  seed  in  this  solution  for  10  minutes;  after  removing  the  seed  from  the 
solution  cover  it  with  canvas  or  sacks  for  2  hours,  ventilate,  thoroughly  dry  and 
sow  within  48  hours. 

The  seed  may  be  dipped  in  half  filled  sacks  or  butts  tied  at  the  end  or  passed 
loose  through  a  formaldehyde  dipping  machine. 

This  practice  may  be  varied  with  equally  good  results  by  wetting 
with  a  sprinkling  can  the  pile  of  seed,  using  the  same  strength  of 
solution.  The  seed  should  be  constantly  shovelled  over  while  being 
sprinkled  until  the  whole  mass  is  thoroughly  wetted.  The  pile  should 
then  be  covered  for  at  least  two  hours.  Dipping  the  butts  or  half-filled 
sacks  in  tubs  or  troughs  as  is  done  with  the  bluestone  solution  may  be 
successfully  practiced. 

A  number  of  hand  and  power  driven  machines  for  cleaning  out 
smut  balls  and  trash,  and  for  dipping  the  seed  in  formaldehyde  solu- 
tion are  on  the  market.  These  machines  may  be  used  to  wash  the 
formaldehyde-treated  seed  when  it  is  to  be  stored  for  a  period  of  time, 
or  planted  in  dry  soil. 

When  formaldehyde-treated  seed  is  stored  for  a  period  longer  than 
48  hours  injury  to  seed  germination  may  result.  It  appears  that  the 
formaldehyde  solution  on  the  seed  rapidly  evaporates,  leaving  behind 
a  residue  of  para-formaldehyde  which  is  very  destructive  to  seed 
germs.  If  formaldehyde-treated  seed  is  stored  and  allowed  to  dry, 
or  when  it  is  sown  in  soil  too  dr}^  to  sprout,  seed  injury  frequently 
may  occur.  This  injury  often  results  in  the  death  of  the  seed  germ. 
Many  of  the  remaining  seedlings  may  appear  contorted  and  bent, 
producing  poor  plants.  These  injuries  do  not  occur  when  the  for- 
maldehyde-treated seed  is  planted  in  soil  sufficiently  moist  to  sprout 
the  seed  promptly. 

Bluestone  and  Formaldehyde  Solutions  Compared. — Bluestone  and 
formaldehyde  are  both  effective  in  destroying  smut  spores. 

"Wheat  which  is  visibly  blackened  with  smut  spores  or  which  con- 
tains smut  balls  in  large  amounts,  should  not  be  used  for  seed  purposes 
because  no  method  of  seed  treatment  has  been  found  wholly  effective 
with  such  badly  infested  lots. 

Solutions  of  bluestone  and  formaldehyde  do  not  deteriorate  on 
standing  but  become  more  concentrated  through  evaporation. 


8 

Both  fungicides  will  destroy  or  injure  the  germs  of  seed  if  the 
solutions  are  concentrated  beyond  the  strength  given  in  the  formulas. 

When  the  seed  coat  is  perfect,  bluestone  cannot  injure  the  germ 
if  the  recommended  formula  is  used.  Formaldehyde,  on  the  contrary, 
appears  to  cause  injury  even  when  the  seed  coats  are  perfect  if  the 
solution  is  too  strong. 

With  slightly  injured  seed  coats,  formaldehyde  causes  less  injury 
than  bluestone.  Bluestone  injury  is  almost  entirely  eliminated  when 
the  seed  is  dipped  in  a  lime  solution  after  the  bluestone  dip. 

Delayed  germination  is  caused  by  both  solutions.  This  is  accentu- 
ated when  the  seeding  occurs  in  cold  wet  weather. 

Formaldehyde  injury  to  cereal  seedlings  is  shown  in  the  delayed 
growth  of  the  plumule  which  may  appear  curved  and  distorted. 
Instead  of  leaving  the  germ  at  nearest  contact  with  the  endosperm, 
the  plumule  may  pass  under  the  seed  coat  escaping  at  the  brush  end 
of  the  kernel.  The  bluestone  solution,  on  the  contrary,  causes  delayed 
germination  of  the  primary  rootlets,  while  the  plumule  behaves  almost 
normally.    This  delayed  root  germination  is  corrected  by  the  lime  dip. 

Both  wheat  and  barley  seed  treated  with  the  bluestone-lime  solu- 
tions and  thoroughly  dried,  may  be  stored  and  kept  for  at  least  two 
years  without  deterioration  greater  than  that  for  untreated  seed  of 
the  same  lot.  Formaldehyde-treated  seed  cannot  be  stored  for  a 
period  longer  than  48  hours  without  liability  to  severe  loss  in  seed 
germination. 

Seed  treated  by  the  bluestone-lime  method  may  be  planted  in  dry 
soil  where  it  remains  in  as  good  condition  as  untreated  seed,  awaiting 
the  rain.  Formaldehyde-treated  seed,  on  the  contrary,  may  be  badly 
injured  by  the  deposits  of  para-formaldehyde  which  appear  immedi- 
ately on  the  evaporation  of  the  formaldehyde  solution. 

With  badly  smutted  lots  of  seed  the  effectiveness  of  both  formalde- 
hyde and  bluestone  as  fungicides  is  greatly  enhanced  by  a  previous 
washing  of  the  smutty  seed  to  remove  smut  balls  and  to  wash  away 
and  disperse  masses  of  spores. 

Washing  the  seed  in  water  previous  to  dipping  in  either  fungicidal 
solution,  prevents  a  great  amount  of  seed  germ  injury,  especially 
when  bluestone  is  used  alone.  Washing  formaldehyde-treated  seed 
immediately  after  removing  the  covering,  two  hours  after  dipping, 
prevents  seed  injury  when  the  seed  is  to  be  stored  or  planted  in 
dry  soil. 

Where  stinking  smut  of  wheat  comes  from  soil  infestation  the 
bluestone-lime  or  bluestone  formulas  are  recommended,  as  formalde- 
hyde evaporates  rapidly  and  has  no  lasting  residual  effect  against 
smut  infection. 

The  bluestone-lime  method  is  more  expensive  than  formaldehyde, 
in  cost  of  materials  and  labor,  but  is  indispensable  in  regions  where 
soil  infestation  exists  or  dry  seeding  occurs.  This  is  especially  true 
in  the  interior  valleys  where  summer  fallowing  is  the  common  practice. 

For  covered  smut  of  barley  formaldehyde  is  preferred,  but  the 
bluestone-lime  solution  may  be  successfully  used.  For  hidden  smut 
of  oats,  kernel  smut  of  sorghum,  and  Sudan  smut,  formaldehyde  alone 
is  recommended. 


